Medication is often dispensed using a unit dose cartridge, such as an ampule or syringe, and a syringe holder or adapter. The cartridge is typically a barrel having a needle at one end and a piston at the other end. Alternatively, the cartridge may include a rubber stopper instead of a needle, or may include a plunger assembly attached to the piston. The syringe adapter is typically a hollow body adapted to hold the cartridge, including a plunger to engage and move the piston in the cartridge.
Because of the threat of communicable diseases, a number of syringes and adapters have been developed to prevent accidental needle sticks or inadvertent reuse of needle devices. Many of these devices, however, are not easy to use or are complicated to manufacture, resulting in less effective disposable syringe devices.
For example, U.S. Pat. No. 5,569,211 discloses a syringe that allows the needle of the syringe to be withdrawn into the barrel of the syringe after medication is dispensed from it. This device, however, is a specially designed substitute for a conventional syringe, and cannot be used to hold commercially available unit dose cartridges.
U.S. Pat. No. 5,522,812 discloses a complicated syringe shield device for holding a conventional ampule not having its own needle. The device has a number of complicated parts, including a cylindrical body, a double needle assembly, a cylindrical shield, a special collar piece allowing the shield to be drawn over the needle and locked, and a plunger assembly, resulting in a device that is potentially difficult and expensive to manufacture. The device also requires two hands to operate, one to hold the body, and one to rotate the shield into the locked position, causing inconvenience to the medical professional using the device.
Another consideration with unit dose cartridges is that they are often made from glass, particularly for holding certain vaccines or biotech drugs where concern about micro-organisms or other contaminants is most critical. Glass cartridges are very fragile and often break during transportation or use. Some existing adapters may not adequately protect the cartridge contained therein from such risks. Others provide greater protection for the cartridge, but may obstruct the professional's view of the cartridge when the device is being used, hampering monitoring of the medication being delivered.
Therefore, there is a need for an improved safety syringe which is inexpensive and simple to manufacture.
In addition, there is a need for a safety syringe adapter which provides improved protection for the cartridge therein, but allows effective observation of the cartridge and the medication being dispensed.